1. Field of the Invention
The present invention relates to an inclination calculation apparatus and an inclination calculation program, and more specifically to an inclination calculation apparatus and an inclination calculation program for calculating an inclination of an input device using an output from an acceleration detection device included in the input device.
2. Description of the Background Art
Conventionally, technologies for calculating an inclination of a device including acceleration detection means have been proposed. For example, patent document 1 (Japanese Laid-Open Patent Publication No. 2001-159951) describes an information processing device including acceleration detection means. In this information processing device, an inclination of the device is calculated from an acceleration detected by the acceleration detection means (an angle of the device with respect to a direction of gravity), and an operation command is generated using the calculated inclination.
This information processing device has a built-in two-axial acceleration sensor. The inclination angle of the device is calculated from a component of the acceleration which is detected in two axial directions when the device is inclined. If the detected acceleration represents only an acceleration of gravity, the inclination of the device can be accurately calculated from the detected acceleration. However, the detected acceleration possibly includes an acceleration of a noise component provided by vibration of the hand of a user or the like in addition to the acceleration of gravity. Therefore, the device described in the above-mentioned publication executes processing of extracting a low-frequency component of the detected acceleration; for example, the device calculates a time average of the detected acceleration. In addition, this information processing device assumes that a change in the acceleration caused by a motion of a human being is smooth and slow. When the low-frequency component does not change during a predetermined pause period, the device determines that the user has performed some operation on the device and processes to change a value to be output as an inclination of the device (inclination operation information). By such processing, the acceleration of the noise component is eliminated from the acceleration detected by the acceleration detection means (acceleration sensor), and thus the inclination of the device can be calculated.
According to the technology described in patent document 1, the device executes the processing of calculating a time average and the processing of determining whether or not the detected acceleration has changed during a predetermined pause period, in order to calculate the inclination of the device. Such processing causes a delay in providing the inclination operation information. In other words, the above-described technology is not capable of calculating the inclination of the device in real time from the detected value of the acceleration. Also according to the technology described in patent document 1, characteristic information to be used for the above-mentioned processing for generating the inclination operation information needs to be prepared in accordance with the type of the operation. Therefore, the contents of the processing needs to be changed in accordance with the characteristic information. This restricts the range of applicable operations and complicates the processing.